Various types of mount structures of an acoustic apparatus to an interior panel of an automobile have been known. In U.S. Pat. No. 4,211,976, issued July 8, 1980, entitled "COMPOUND ACOUSTIC APPARATUS FOR AUTOMOTIVE VEHICLES" and owned by the assignee of the present invention, an acoustic apparatus is mounted from behind the interior panel into a rectangular aperture formed in the interior panel and only the operating section of the acoustic apparatus projects to the front through the aperture. The front of the acoustic apparatus housing is abutted against the rear surface of the interior panel and they are firmly fixed to each other. In this rear surface mount structure, it is impossible to draw out the acoustic apparatus into the room of the automobile without removing the interior panel, and therefore the protection against the theft of the acoustic apparatus is required little. However, in this type of a mount structure, it is very cumbersome to install the acoustic apparatus.
Many of recent acoustic apparatuses for automobiles use a front mount structure wherein the acoustic apparatus is mounted from the front of an interior panel into a rectangular aperture formed in the interior panel. In this type of a mount structure, the acoustic apparatus housing is made to have a size to be inserted through the rectangular aperture formed in the interior panel and is fixed to the interior panel with the housing inserted in the aperture. A mount structure where mount springs engageable with the rear surface of the interior panel are provided on the opposite side surfaces of an acoustic apparatus housing in one of the well known fashions of a front mount structure. In this structure, if the acoustic apparatus is once mounted into the interior panel, it is not easy to take out the acoustic apparatus from the interior panel and this is desirable in view of the prevention of theft, but the maintenance and inspection or repair of the acoustic apparatus become difficult. It is also known that the front section of an acoustic apparatus housing is formed with a flange section larger than the rectangular aperture and the flange section is fixed to the front surface of the interior panel by screws. A mount structure where wedge members engageable with the rear surface of the interior panel are provided on opposite side surfaces of an acoustic apparatus housing such that they can be depressed, and the wedge members are moved by rotating operating screws secured to the front surface of the acoustic apparatus housing is also known. This wedge type front mount structure is disclosed, for example, in Japanese Laid-Open Patent Application No. 61-53797, laid open on Mar. 17, 1986, and owned by the assignee of the present invention. While the mount structure wherein screws are operated on the front side of the interior panel can facilitate the attachment and detachment of the acoustic apparatus to and from the interior panel, there are many chances that the acoustic apparatus may be stolen.
U.S. Pat. No. 4,494,114, issued on Jan. 15, 1985 and entitled "SECURITY ARRANGEMENT FOR AND METHOD OF RENDERING MICROPROCESSOR-CONTROLLED ELECTRONIC EQUIPMENT INOPERATIVE AFTER OCCURRENCE OF DISABLING EVENT" has suggested an acoustic apparatus for automobiles that has a microprocessor for rendering the acoustic apparatus inoperative when the acoustic apparatus is moved mechanically from the interior panel. Although this suggestion is quite unique and is quite effective in practice, the cost of the produced acoustic apparatus is high.